#include <iostream>

using namespace std;

typedef long long LL;

const int N = 1e7 + 10, M = 1e4 + 10;
LL f[N], v[M], w[M], t, n;

int main()
{
	cin >> t >> n;
	for(int i = 1; i <= n; i++) cin >> v[i] >> w[i];
	
	for(int i = 1; i <= n; i++)
	{
		for(int j = v[i]; j <= t; j++)
		{
			f[j] = max(f[j], f[j - v[i]] + w[i]);
		}
	}
	cout << f[t] << endl;
	return 0;
}
